Endoscopic inspection is a common practice in the medical diagnosis of gastro-intestinal (G.I.) diseases. The video camera used for identifying observable irregularities of the internal lining of the G.I. tract is installed within an endoscope and progressive scenes are observed by pushing the endoscope inside the tract. The endoscope is a tubular device typically containing either a camera with the associated electric circuits or a fiber-optic image guide. It also includes a light source or a light guide, and an electrical conductor for accepting signals and/or supplying energy. Because the movement of the endoscope head along the G.I. tract is brought about by a pushing action, the mechanical impact associated with such application of force become especially adverse as soon as the head of the endoscope enters a bend. In such bends, the movement of the endoscope is greatly impeded, risking the G.I. tract walls, which are susceptible to perforation, and limiting the method of endoscopic inspection to non-convoluted regions of the G.I. tract.
An in-vivo autonomous video capsule, described in U.S. Pat. No. 5,604,531 whose disclosure is incorporated herein by reference, moves along the G.I. tract by virtue of the natural squeezing action of the tract's walls, thus overcoming the risk of the pushing action, and, in addition, offering a more convenient method of administering the camera. An additional benefit of the capsule is avoiding the cumbersome aspects of connecting the intestines of the patient to external appliances. Via the autonomous capsule, images of the gastro-intestinal tract are obtained without physical connections being made to an energy source or an information drain. An internal power supply energizes the capsule and supports the illumination, image acquisition and radio transmission of the information to an external receiver. Because of the considerable length of the G.I. tract, many images have to be acquired in order to cover the entire length of the tract, this amount of data may be augmented by redundant images of the same site which are acquired when the capsule stops moving or is only barely doing so. Such a task consumes a substantial amount of energy, thus potentially becoming a limiting factor in respect of quality and quantity of the set of images collected in a single inspection. An additional drawback connected with redundancy of images of a G.I. tract is the effectivity of analysis stage. Once the entire sequence of images is presented to the analyzing physician, a lengthy process of finding the potential sites of interest ensues. Any redundancy existing in such a sequence of images poses a disturbance to analysis procedure.